Subtraction and Negative Numbers

Oct 13, 2025 by wbrum.org 53 views

When dealing with mathematical expressions, it's essential to follow the correct order of operations to avoid confusion and ensure accurate results. In this article, we'll explore the concept of the order of operations and apply it to a specific problem involving subtraction and negative numbers.

The Order of Operations

The order of operations is a set of rules that dictates the order in which mathematical operations should be performed when there are multiple operations in an expression. The acronym PEMDAS is commonly used to remember the order of operations:

Parentheses: Evaluate expressions inside parentheses first.
Exponents: Evaluate any exponential expressions next.
Multiplication and Division: Evaluate multiplication and division operations from left to right.
Addition and Subtraction: Finally, evaluate any addition and subtraction operations from left to right.

Subtraction and Negative Numbers

When dealing with subtraction and negative numbers, it's crucial to understand the concept of the "double negative." A double negative occurs when a negative number is subtracted from another negative number, or when a negative number is multiplied by another negative number.

In the case of the expression $9 - (-5)$ , we need to apply the order of operations to evaluate the expression correctly.

Evaluating the Expression

To evaluate the expression $9 - (-5)$ , we need to follow the order of operations:

Evaluate the expression inside the parentheses: $-5$
Since there are no exponents, we can move on to the next step.
We need to subtract $-5$ from $9$ . However, when subtracting a negative number, we need to change the subtraction sign to an addition sign.
Therefore, the expression becomes $9 + 5$ .

Conclusion

In conclusion, when evaluating the expression $9 - (-5)$ , we need to apply the order of operations and change the subtraction sign to an addition sign when subtracting a negative number. The correct answer is $9 + 5$ .

Comparison with Other Options

Let's compare the correct answer with the other options:

A. $-9 + 5$ : This option is incorrect because it changes the order of operations and does not follow the correct procedure for subtracting a negative number.
B. $9 - 5$ : This option is incorrect because it does not account for the double negative in the original expression.
C. $-9 - 5$ : This option is incorrect because it changes the order of operations and does not follow the correct procedure for subtracting a negative number.

Real-World Applications

Understanding the order of operations and how to handle subtraction and negative numbers is crucial in various real-world applications, such as:

Financial calculations: When dealing with financial transactions, it's essential to follow the correct order of operations to ensure accurate results.
Scientific calculations: In scientific calculations, the order of operations is critical to ensure accurate results and avoid errors.
Programming: In programming, the order of operations is essential to write efficient and accurate code.

Conclusion

In this article, we'll address some common questions and concerns related to the order of operations and subtraction with negative numbers.

Q: What is the order of operations?

A: The order of operations is a set of rules that dictates the order in which mathematical operations should be performed when there are multiple operations in an expression. The acronym PEMDAS is commonly used to remember the order of operations:

Parentheses: Evaluate expressions inside parentheses first.
Exponents: Evaluate any exponential expressions next.
Multiplication and Division: Evaluate multiplication and division operations from left to right.
Addition and Subtraction: Finally, evaluate any addition and subtraction operations from left to right.

Q: What is a double negative?

A: A double negative occurs when a negative number is subtracted from another negative number, or when a negative number is multiplied by another negative number.

Q: How do I evaluate an expression with a double negative?

A: When evaluating an expression with a double negative, you need to change the subtraction sign to an addition sign. For example, in the expression $9 - (-5)$ , you would change the subtraction sign to an addition sign, resulting in $9 + 5$ .

Q: What is the difference between subtracting a negative number and adding a positive number?

A: When you subtract a negative number, you are essentially adding a positive number. For example, $9 - (-5)$ is equivalent to $9 + 5$ .

Q: Can you provide more examples of evaluating expressions with double negatives?

A: Here are a few more examples:

$5 - (-3) = 5 + 3 = 8$
$-2 - (-4) = -2 + 4 = 2$
$-1 - (-6) = -1 + 6 = 5$

Q: How do I apply the order of operations to evaluate expressions with multiple operations?

A: To apply the order of operations, follow these steps:

Evaluate expressions inside parentheses first.
Evaluate any exponential expressions next.
Evaluate multiplication and division operations from left to right.
Finally, evaluate any addition and subtraction operations from left to right.

Q: Can you provide an example of applying the order of operations to evaluate an expression?

A: Here's an example:

$3 \times 2 + 12 - 5$

To evaluate this expression, follow the order of operations:

Evaluate the multiplication operation: $3 \times 2 = 6$
Evaluate the addition operation: $6 + 12 = 18$
Finally, evaluate the subtraction operation: $18 - 5 = 13$

Therefore, the final answer is $13$ .

Q: Why is it essential to follow the order of operations?

A: Following the order of operations ensures that mathematical expressions are evaluated correctly and consistently. It helps to avoid errors and confusion, and ensures that mathematical results are accurate and reliable.

Q: Can you provide more resources for learning about the order of operations and subtraction with negative numbers?

A: Here are a few resources to get you started:

Khan Academy: Order of Operations
Mathway: Order of Operations
Purplemath: Order of Operations
Math Open Reference: Order of Operations

Remember, practice makes perfect! The more you practice evaluating expressions with the order of operations, the more comfortable you'll become with the rules and procedures.